Abstract:

Wang Yinjuan*, Gu Hua, Guo Meihua, Tu Ying, He Li. *Department of Dermatology, First Affiliated Hospital of Kunming Medical University, Kunming 650032, China. Corresponding author: He Li, Email: helikm2662@126.com 【Abstract】 Objective To investigate the relationship of Toll-like receptors （TLRs） 2 and 4 with the occurrence of chloasma. Methods Peripheral blood samples were collected from 40 patients with chloasma and 40 healthy human controls, and skin samples were also collected from the lesions of 10 of the patients and normal skin of 10 of the healthy controls. Real time （RT）-PCR was performed to measure the mRNA expressions of TLR2 and TLR4 in skin lesions and blood samples. An immunohistochemical test was conducted to observe the expressions of TLR2 and TLR4 in skin lesions. Statistical analysis was carried out by t test. Results The expressions of TLR2 and TLR4 mRNAs were both significantly higher in skin lesions of the patients than in normal skin of the controls （9.72 ± 2.93 vs. 5.10 ± 2.69, t = 3.67, P < 0.01; 9.52 ± 2.88 vs. 4.77 ± 1.90, t = 4.36, P < 0.01）, while no significant difference was found in the mRNA expressions of TLR2 or TLR4 in peripheral blood between the patients and controls （both P > 0.05）. As the immunohistochemical test revealed, TLR2 was absent in both the epidermis and vascular endothelial cells in 6 normal control skin samples, weakly expressed in the basal layer of the epidermis but absent in vascular endothelial cells in 4 normal skin samples, and no TLR4 expression was observed in either the epidermis or vascular endothelial cells in these control skin samples. Among the 10 skin samples from chloasma lesions, 3 showed TLR2 expression in the whole epidermis, 7 in both basal cell layer and prickle cell layer but not in vascular endothelial cells in the superficial dermal layer, all showed strong TLR4 expression in the basal cell layer and weak TLR4 expression in the prickle cell layer, and 3 exhibited TLR4 expression in vascular endothelial cells in the superficial dermal layer. Conclusion TLR-mediated immune responses in local skin might be related to the occurrence of chloasma.